本文構建了一個簡化模型，考慮在共同所有權下兩個競爭零售商之間的相互推薦關係。藉由檢驗較低品質改變的效果和機構投資人持有這兩個零售商股份比例的影響，主要的發現為共同所有權增強了正面影響並減輕了負面影響。特別是共同所有權提高了品質的門檻，為零售商提供了更多改進的空間。然而，如果較低品質過高，這種效果會消失。另一方面，共同所有權為零售商創造誘因去最大化其股東利益。最後，共同所有權也影響福利，研究顯示只有單位成本的增加，但低於一個特定門檻，才能改善整體社會福利。

This paper constructs a stylized model that considers the relationship of mutual referral between two competing retailers under common ownership. The main findings indicate that common ownership enhances the positive impacts and mitigates the negative impacts on both prices and profits by examining the effects of changes in lower quality and the ratio of these two retailers’ shares held by the institutional investors. In particular, common ownership increases the threshold of quality, providing retailers with more room to improve. However, this effect disappears if the lower quality is too high. On the other hand, common ownership may create an incentive for retailers to maximize their shareholders’ interests. Finally, common ownership also impacts welfare, which shows that only an increase in unit costs, but lower than a certain threshold, can improve overall social welfare.

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